Bring sugar, butter, and evaporated milk to a rolling boil in a large (mine is 2 and 3/4-quart-sized) saucepan on medium heat.
Stir the mixture constantly.
Keep stirring and boil for 4 minutes or until a candy thermometer reaches 234 degrees.
Remove the pan from the heat.
Stir in the peanut butter and marshmallow creme and keep stirring until both are melted. Add vanilla and mix well.
Pour into pan, spreading to cover the pan completely.
Cool for an hour before scooping the filling into balls for making the white chocolate peanut butter buckeyes or truffles.
Line a baking sheet with wax paper. Using the 100-sized scooper, drop scoops of the mixture onto the baking sheet. If the mixture is too soft, stick the pan of peanut butter fudge filling in the freezer for 5 minutes. (You do not want to have the mixture harden too much or it will be difficult to scoop.) When the pan is filled with rounded scoops of peanut butter fudge, place it in the freezer for 15 minutes.
While the peanut butter scoops are chilling, heat water in a saucepan. Place a mixing bowl over the hot (not boiling) water. Melt the white chocolate chips and shortening, stirring until smooth. Slow and easy is the key here. If you have to add a bit more shortening for a smoother consistency, go right ahead.
If you are making white chocolate peanut butter truffles, save the scrapings from the pan (you can leave them in the pan) for using as little peanut butter dollops on top of the finished truffles for decorating purposes.